Adaptive network content delivery system

ABSTRACT

A method and apparatus stores media content in a variety of storage devices, with at least a portion of the storage devices having different performance characteristics. The system can deliver media to a large number of clients while maintaining a high level of viewing experience for each client by automatically adapting the bit rate of a media being delivered to a client using the client&#39;s last mile bit rate variation. The system provides clients with smooth viewing of video without buffering stops. The client does not need a custom video content player to communicate with the system.

CROSS-REFERENCE TO RELATED APPLICATIONS Priority Claim

This application claims benefit of U.S. Provisional Application Nos.61/117, 505, filed Nov. 24, 2008, 61/161,376, filed Mar. 18, 2009, and61/166,423, filed Apr. 3, 2009 the entire contents of each is herebyincorporated by reference as if fully set forth herein, under 35 U.S.C.§119(e).

TECHNICAL FIELD

The present disclosure generally relates to media content delivery.

BACKGROUND

The approaches described in this section could be pursued, but are notnecessarily approaches that have been previously conceived or pursued.Therefore, unless otherwise indicated herein, the approaches describedin this section are not prior art to the claims in this application andare not admitted to be prior art by inclusion in this section.

Delivery of content across the Internet has been accomplished in severaldifferent ways. Content servers have been used to deliver contentdirectly to requesting clients. As the content servers became overloadedfrom the traffic demands, mirroring of the content across multipleservers were implemented. Mirror servers were added as client trafficincreased beyond the capacity of the installed base of mirror servers.

As mirroring became costly to the content providers, caching content incontent delivery networks (CDN) became popular. The content provider'scontent was distributed among caching servers across the Internet. Thecaching servers were shared among multiple content providers andoperated by a CDN provider. The caching servers were essentially fileservers that served different types of files to client systems.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings and in whichlike reference numerals refer to similar elements and in which:

FIG. 1 illustrates a media flow director (MFD) in communication withclient systems, an origin server, a peer MFD, and a central managementstation across a network, according to an embodiment of the invention;

FIG. 2 illustrates an example of an MFD component and data flowarchitecture, according to an embodiment of the invention;

FIG. 3 illustrates an example of dynamically determining the popularityof portions of content, according to an embodiment of the invention;

FIG. 4 illustrates a MFD deployment that replaces a conventional videoserver site, according to an embodiment of the invention;

FIG. 5 illustrates an MFD network delivering content to client systems,according to an embodiment of the invention;

FIG. 6 illustrates a computer system upon which an embodiment may beimplemented;

FIG. 7 illustrates flow diagram of the workflow between the HPE and theserver side player, according to an embodiment of the invention;

FIG. 8 a illustrates the interaction between a disk manager and a policymodule and an analytics module, according to an embodiment of theinvention;

FIG. 8 b illustrates the interaction between a disk manager anddictionaries for storage devices, according to an embodiment of theinvention;

FIG. 8 c illustrates the interaction between a disk manager and areverse block map, according to an embodiment of the invention;

FIG. 9 illustrates the interaction between a buffer pool and buffermanager, according to an embodiment of the invention;

FIG. 10 a illustrates the interaction between a media manager, buffermanager, and media providers, according to an embodiment of theinvention;

FIG. 10 b illustrates the interaction between a media manager andanalytics module for determining hot video segments, according to anembodiment of the invention;

FIG. 11 illustrates a flow chart of a network manager in a MFD,according to an embodiment of the invention;

FIG. 12 illustrates a progressive download hint track location in acontainer file, according to an embodiment of the invention;

FIG. 13 illustrates a graphical user interface screenshot of a parameterspecification screen, according to an embodiment of the invention;

FIG. 14 illustrates a graphical user interface screenshot of a real timebyte delivery monitoring graph, according to an embodiment of theinvention; and

FIG. 15 illustrates a graphical user interface screenshot of a networkconnection performance monitoring graph, according to an embodiment ofthe invention.

DETAILED DESCRIPTION

An adaptive network content delivery system is described. In thefollowing description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. It will be apparent, however, toone skilled in the art that the present invention may be practicedwithout these specific details. In other instances, well-knownstructures and devices are shown in block diagram form in order to avoidunnecessarily obscuring the present invention.

Embodiments are described herein according to the following outline:

1.0 General Overview 2.0 Structural and Functional Overview

3.0 Adaptive Content Delivery over a Network

3.1 Media Flow Director Architecture 3.2 Media Flow Director Placement4.0 Implementation Mechanisms—Hardware Overview 5.0 Examples 6.0Extensions and Alternatives 1.0 GENERAL OVERVIEW

A method for an adaptive network content delivery system is described.In other embodiments, the invention encompasses a computer apparatus anda computer-readable medium configured to carry out the foregoing steps.

2.0 STRUCTURAL AND FUNCTIONAL OVERVIEW

An adaptive network content delivery system is described. Referring toFIG. 1, a possible embodiment provides a media flow director (MFD) 103.A MFD is a network device that can efficiently deliver video content(and other types of file content of various sizes, e.g., media (audio,pictures, etc.), games, software, HTML, scripts, etc.) over a network104 to a plurality of clients 101 a, 101 b, 101 n, via HTTP, FTP,streaming, or other protocols. Video content includes such content asfeature length movies, sitcoms, variety shows, talk shows, news shows,advertisements, etc. Client devices 101 a, 101 b, 101 n, may be apersonal computing device such as a desktop or laptop computer, set topbox, handheld computing device, cellular phone, portable media player,or any other portable device capable of displaying multimedia content,and are also coupled to network 104 through any proper interface.

The MFD 103 stores video content internally in a variety of storagedevices, including HDD, SSD, RAM, non-volatile memory, etc. The MFD 103can deliver video to a large number of clients while maintaining a highlevel of viewing experience for each client. The MFD 103 automaticallyadapts the bit rate of a video being delivered to a client 101 bymeasuring the client's last mile bit rate variation. The MFD providesthe clients with smooth viewing of video without buffering stops. Itassures delivery of in-progress videos to clients using the adaptive bitrate delivery. The MFD dynamically adapts the bit rate of the video tomatch the effective last mile bandwidth and to adapt to changing networkconditions for the client. The MFD can dynamically measure the last milebandwidth to the client in order to dynamically adjust the bit rate. Theclient does not need a custom video content player to communicate withthe MFD. The MFD supports industry standard video players such as Flash,Quicktime, SilverLight, Windows Media Player, etc.

The MFD 103 provides policy controls on the storage and delivery ofvideos that can be defined by a customer as well as the MFD provider.The MFD can be deployed in a variety of ways across the network 104,including at an edge cache location or an origin server location. Thenetwork 104 may be implemented by any medium or mechanism that providesfor the exchange of data between devices in the communication system.Examples of network 104 include, without limitation, a network such as aLocal Area Network (LAN), Wide Area Network (WAN), Ethernet, intranet,the Internet, or one or more terrestrial, satellite or wireless links.

The MFD 103 communicates with network 104 through any propercommunication interface, such as an Ethernet or wireless communicationsport. Alternatively or in addition, any number of devices connected tonetwork 104 may also be directly connected to each other through acommunications link. For example, the MFD 103 can request content froman origin server 102 via the network 104 or via a local network in orderto obtain URL content when a client 101 requests a URL content that theMFD 103 does not have stored in its memory. Additionally, MFD 103 cancommunicate with another MFD 105 via the network 104 or via a localnetwork in order to obtain URL content, MFD content information, MFDstatus, etc.

A central management station 106 may be available to allowadministrators to set policies for MFD management such as cachemanagement, bandwidth limitations, content popularity determination,etc. The central management station 106 also allows administrators tomanage where and how content is stored in the multiple storage deviceswithin a MFD. The central management station 106 may communicate via alocal network or connection to MFDs 103, 105 or via network 104. Anadministrator logs into the central management system 106 and selects aMFD or set of MFDs that the administrator wants to interact with. Theadministrator can define policies and have the policies sent to a MFD orpushed out to multiple MFDs by the central management station 106.Alternatively, the MFDs may contact the central management station 106periodically or when notified that by the central management stationthat updates are available for that MFD.

3.0 ADAPTIVE CONTENT DELIVERY OVER A NETWORK

3.1 Media Flow Director Architecture

FIG. 2 illustrates a possible embodiment showing the architecture of acontent delivery switch that is configured as a MFD to deliver videocontent. The components in the architecture are described below.

Output Protocol Engine 210

The output protocol engine 210 handles requests from clients. A clientsends a request to the MFD to make a connection with client, e.g., anHTTP get request for a particular URL, the output protocol engine 210passes for requests URL content to the server side player 201.

Server Side Player 201

The server side player 201 is primarily responsible for theencapsulation and enforcement of video specific logic for each videostream. Such an enforcement could happen both at the inbound side when arequest is made to the MFD for a video stream or at the outbound sidewhen a specific video stream is heading out for delivery.

The server side player 201 interprets a URL received from the outputprotocol engine 210, decides what bit rate is to be used for therequested video content, handles what is to be sent, and where to playthe video from (what frame within the video to start streaming from).The server side player 201 is bit rate aware and knows the bit rate ofthe video content that it is trying to serve. It can use informationobtained from the optimized network stack 211 to find out what theeffective bandwidth is for the client in the last mile. The server sideplayer 201 can also authorize the request. In a possible embodiment, asigned hash key embedded as a query string in the URL is used to verifythat the request is authorized.

The server side player 201 provides an assured bit rate and quality ofservice (QoS) feature. If the client has to buffer, then it means thatthe MFD has fallen behind in its delivery rate and the client hasexperienced a dead period where there is no content to play or display.In one possible embodiment, the server side player 201 calculates howmuch data has been sent to the client and how much time has passed. Theserver side player 201 tracks the amount of data sent to each client andthe bit rate of the video content that each client is being sent. Aseach client is sent an amount of data, the server side player 201records the amount of data that was sent and the amount of time that haspassed since the last amount of data was sent. Alternatively, the serverside player 201 can record the total amount of data sent to the clientand the total amount of time that has passed during the client'ssession. Using the recorded information, the server side player 201 cancalculate if it has fallen behind in its delivery to a particularclient. For example, if the server side player 201 has sent 30 secondsof data at a certain bit rate to the client and 31 seconds have elapsedsince the last transmission of data, the server side player 201 knowsthat it has fallen behind.

In another possible embodiment, the server side player 201 calculateshow much more data it needs to deliver to the client and the time windowthat the data must be delivered in to avoid buffering on the clientside. This calculation is slightly different than the previous example.The server side player 201 knows the size of the video file and thus cancalculate the amount of data that remains to be sent to the client. Itcan also calculate the amount of time it has to deliver the remainingamount of data given the bit rate and the total size of the video file.The server side player 201 can calculate the deadline that it needs toset for a task that it creates to deliver a segment of the video file tothe client.

The MFD is a task-based system that can use deadline-based scheduling.The server side player 201 sets up deadlines in the tasks that itcreates in order to avoid client buffering.

In a possible embodiment, the server side player 201 calculates anassured flow rate (AFR) value (described below). The AFR is thetransmission rate required to ensure a smooth viewing experience. Theserver side player 201 uses the AFR value to set deadlines for tasksthat it creates for requesting data from the buffer manager 203. Theserver side player 201 calculates the AFR and the output protocol engine210 manages the transmission rate on each connection based on the AFRand sets the task deadlines such that the AFR can be met. In the exampleabove, the server side player 201 tries to stay ahead of the AFR andwould know that it has fallen behind if, for example, the server sideplayer 201 has sent 30 seconds of data and 30 seconds have elapsed sincethe last transmission, the server side player 201 immediately knows thatit has fallen behind. In an alternative embodiment, the server sideplayer 201 can scan a media file to set an AFR for the media file. Theserver side player 201 knows that a certain quality or resolution of themedia file requires a certain transmission rate in order to ensure thatthe client will not stall.

The server side player 201 also handles scrubbing requests (in order todecide what to do in the future), transcoding, and ad insertion. Theserver side player 201 is video-aware as opposed to a typical fileserver that does not know what the video file format or video contentis. When the server side player 201 changes the bit rate after the videohas started, the server side player 201 already knows where theassociated frame exists in the different bit rate version, so the serverside player 201 can easily change bit rates without the client having tosend a different offset for the new bit rate. A possible embodimentstores video content in a custom format that can be transcoded to anybit rate that it requires. This allows the server side player 201 toknow exactly where the associated frame is for each bit ratetranscoding. Another possible embodiment stores several different bitrate versions for a specific video content. The server side player 201stores index tables for each of the bit rate versions so the server sideplayer 201 can quickly refer to a table to find the associated frame forthe new bit rate video.

The server side player 201 can perform advertisement insertion into thevideo streams. Ads can be placed in the video stream as overlays. Thismakes the ad insertion independent of the client player. The content canbe dynamically created, e.g., subtitle language selection can be made onthe fly and the appropriate subtitles can be overlaid on the fly. Theserver side player 201 can splice an ad into the middle of a video(referred to as mid-roll). The server side player 201 can also overwritethe voice channel of a video with another channel to provide multiplelanguage support without having to store different versions of the videocontent.

In a possible embodiment, the server side player 201 provides twointerfaces, both of which are accessed by the HTTP protocol engine (HPE)in the input protocol engine 209:

northbound interface: This serves as the northbound interface whereevery incoming request parsed by the HPE is examined by the server sideplayer 201 to validate the request with its customer specific logic.Once the request is examined and the necessary parameters are enforced,the request is sent back to the HPE so that it can make a valid requestto the buffer manager 203 (and other providers thereafter) for thecontent.

southbound interface: This serves as the southbound interface where alloutgoing data is sent to server side player 201 to be examined beforedelivery. This is the final place where the server side player 201 canenforce any restrictions before the content is sent out for delivery.The server side player 201 has the ability at this stage to modify thedata buffers returned by the buffer manager 203 if required beforesending it out.

FIG. 7 shows a possible embodiment of the workflow between the HPE andthe server side player 201. The following steps are performed:

Step 1: User request comes to the HPE 701 through the optimized networkstack 211 after a connection has been established.

Step 2: HPE 701 does minimal parsing to get the query string andname/value pairs.

Step 3: HPE 701 then initiates a call to the server side player 201 withthe query string.

Step 3a: Server side player 201 may act as a pass through for files thatare not related to video, but per se security access files, etc such asthose requested by client players.

Step 4: For every first call per new connection, server side player 201remaps the query string to an internal URL pointing to a metafile. Thismetafile stores the number of profiles present, their rates, timeperiod, and other information of the video.

Step 5: Server side player 201 returns the remapped URL to HPE 701 andalso sets a flag that indicates to HPE 701 to not send the returnedmetafile on the wire, but back to the server side player 201 for furtherprocessing.

Step 6: HPE 701 creates a task to fetch the metafile from cache. HPE 701receives the metafile and passes it back to server side player 201.

Step 6a: The server side player 201 stores the information in themetafile in the socket structure for that connection. The metafileinformation is stored in the cache as a result of this fetch for fastlookup in the future.

Step 7: Once the socket structure is populated, server side player 201can now remap the original URL with the translation logic plugin 704.The translation logic plugin 704 (does both seek and rate adaptation)uses the information present in the server side player 201 structure inthe socket connection to do the necessary translation to differentprofiles/chunks.

Step 8: Server side player 201 returns the remapped URL and resets theflag in HPE 701 to convey that it is ok to fetch and send the dataretrieved from the cache on the wire.

Step 9: The query string is passed to the server side player 201. Serverside player 201 checks if the socket structure is already populated.

Step 10: If populated and if the name/value pair for time offset is notminimal (time offsets or byte offsets that denote a scrub or seek arepresent), then server side player 201 calls translation logic to remapto an appropriate URL and server side player 201 calls HPE 701 tofetch/pass data.

Step 11: If name/value pair in query string is minimal (no time offsetsor byte offsets that denote a scrub or seek), then repeat from Step 4.

Scheduler 202

The scheduler 202 uses deadlines set by callers to organize schedulingof tasks. There can be hundreds of thousands of tasks in that thescheduler 202 is managing. It keeps the tasks organized by thedeadlines. The scheduler 202 monitors the tasks to see if any tasks havemissed their deadline. This tells the scheduler 202 that the MFD hasfallen behind. It sends feedback to the server side player 201 to tellit that the delivery rate has fallen behind. The scheduler 202 can sendinformation such as task ID and amount of time that the task missed thedeadline.

In a possible embodiment, the scheduler 202 may refuse to accept a taskfor a new connection if it determines that it cannot meet the requestedtask's deadline. This is one component of admission control that ensuresthat MFD resources are not over-committed and existing connections playsmoothly. Similarly, all components that implement tasks (e.g. buffermanager, disk manager and origin manager) can look at their internalresource commitments and fail the first task of a new connection as away of refusing to accept the session.

The server side player 201 can identify which tasks are associated witheach client. It can calculate, possibly using the above describedcalculations, how late it is in delivering video content to a client andadjust deadlines for subsequent tasks accordingly. The server sideplayer 201 can then stop accepting new connections. In a possibleembodiment, the server side player 201 can, possibly based on policysettings, lower the bit rate of some of the existing connections inorder to accept additional connections. These approaches allow theserver side player 201 to dynamically measure its performance and thusit does not need to set a static cap on the number of clientconnections. Given that it is handling many different bit rates, astatic cap on the number of connections does not represent the actualcapacity of the MFD, so a dynamic cap can be more efficient and allowsthe MFD to decide on its own whether it can handle more or lessconnections.

A possible embodiment performs deadline scheduling where each task statecan have multiple deadline queues. Each deadline queue can correspond tofixed time periods, for example, 1/10 ms chunks. The scheduler 202 canpop the queue that has the shortest deadline.

Task handlers are pre-registered with the scheduler 202 at init time.They are always non-blocking. Blocking handlers are another set ofthreads and are described below. In a possible embodiment, any taskswitching does not involve a thread context switch.

Blocking tasks are given off to a pool of threads. Whenever there is atask to be completed, one thread from the thread pool services the task.The scheduler 202 at this point has handed off the blocking task. Hence,no other tasks will be blocked.

The scheduler checks relevant queues (state/deadline queues) in a WRR(Weighted Round Robin) fashion. It dispatches tasks by callingpre-registered task handlers. The scheduler 202 schedules according to adeadline by keeping track of elapsed time and popping relevant queues.The deadline scheduling is not strictly real time. The deadlines are arecommendation to the scheduler 202 that a particular task needs to bescheduled before another.

The scheduler 202 enables different types of threads. Threads are taskthreads, I/O threads, event threads, and network threads. Theseenumerated threads do not limit the number and types of threads that canbe implemented. Task threads are the primary engines for task execution.The scheduler 202 is the start routine. It implements a dispatch lookbased on priority management. These threads block when there are notasks to run.

I/O threads are used to implement blocking threads (e.g., disk I/O inthe disk manager 206). They can block on read/write calls. Event threadsare asynchronous and map network events to task state changes. Networkthreads implement the user space network stack and typically do notblock on reads. Dedicated threads are used for scaling and management oftimers for AFR. Alternatively, the network activity could be performedusing tasks on the scheduler threads.

Disk Manager 206

The disk manager 206 manages objects spread over multiple disk drives,regardless of size and count and type. Also referring to FIG. 8 a, diskmanager 206 obtains hints about object placement from the policy modules801 (PM) and analytics module 802 (AM). The media manager 204 caninteract with the PM 801 to help it decide how to apportion videos intosegments and also to determine when a portion of a video is determinedas hot (discussed below). The media manager 204 can also interact withthe AM 802. The AM 802 determines which video portions are hot based onthe statistical information covering video portion hits provided by themedia manager 204.

Objects stored within disk manager 206 are most likely video related butcan be anything. The disk layout of objects is particularly suited forvideo objects because they are consumed in a serial fashion. For smallobjects, disk manager 206 performs special packing so many sequential,small objects can be packed closely together in time sequence order.This works very well in the case where the small objects are chunkedpieces of a larger video in time sequence. This packing allows diskmanager 206 to optimize read performance of disk drives because the timeit takes to read a small amount of data is about the same as the time ittakes to read about 1-2 MB of data. In another embodiment, the diskmanager 206 can allow for multiple strategies for packing objects. Inaddition to time based locality, it can also support packing based onlocality within the name structure or other custom schemes.

Referring also to FIG. 8 c, the disk manager 206 can use a reverse blockmap (RBM) 805 in order to consistently read large blocks 806 (even inthe presence of small objects). The block sizes are set to a specificsize that allows for efficient reads from the disk drives, e.g., 1 MB, 2MB, etc. For each block, the disk manager 206 keeps a list of extents inthe RBM 805, where each extent is a contiguous portion of an object. Inthis example, the RBM 805 lists block 806 with related extents 807-812.Note that for smaller objects, multiple small objects themselves orportions of the smaller objects may fit into a block and may be readinto cache memory together. When the disk manager 206 receives a requestfor a specific portion of the object, it locates the block where thespecific portion resides. It then reads the entire block into cachememory 813 supplied by the buffer manager 203. Using the RBM 805, thedisk manager 206 is able to assign the correct identity (UOL) to eachbuffer (as described below). This allows the buffer manager 203 tosubsequently consume the additional data without doing any additional10. In an embodiment, the disk manager 206 creates entries in the RBMfor all of the objects stored in the MDF. The disk manager 206 maycreate an entry in the RBM for an object when the object is loaded froman origin server.

The disk manager 206 accounts for many types of disk controllers anddisk drives, including SATA, SAS, SSD and flash. Each drive type hasdifferent size and performance characteristics. As such, the diskmanager 206 will vary the data layout for each drive type to allowoptimal performance and utilization of disk space. In order to self-tunefor variances in drive types and controllers, the disk manager 206performs a brief bandwidth test on startup, so it can categorize thelarge number of configurations that it sees within an open hardwareframework.

An administrator can configure the disk manager 206 to store contentfrom an origin server onto the hard drive or in a cache. Theadministrator can specify that the disk manager 206 store the content onthe first hit or any specific number of hits before the disk manager 206stores the content on the hard drive or cache. This allows theadministrator the flexibility to adjust the cached content to any knownor predicted demands. Alternatively, how the disk manager 206 stores thecontent can be driven by internal analytics. The administrator caninstruct the disk manager 206 to store specific new content on the harddrive because, for example, he knows that new episodes of a show will bein demand.

Eviction policies are enforced by the disk manager 206. Content can beremoved from the hard drive or cache in order to make room for newcontent based on eviction policies defined by an administrator orcustomer. In a possible embodiment, eviction policies can be internallyderived based on analytical algorithms, e.g., using a least recentlyused (LRU) algorithm or its derivatives. The customer can install enoughstorage capacity in the MFD such that the storage space may never befilled by the customer's content. The customer may desire to have itscontent in the fastest areas of the hard drives and sparsely populatethe hard drives in order to accomplish this goal. The customer can thenhave a set of MFDs dedicated to their hottest content with sparselypopulated hard drives and have another set of MFDs caching theirless-popular content. The administrator can specify that certain harddrives on a MFD are kept sparsely populated with the hottest content andother hard drives on the MFD are used for all other content. This allowsa customer to implement an efficient storage scheme for a particularMFD.

Referring also to FIG. 8 b, the disk manager 206 treats each device asan independent cache module. The meta-data and data on each devicecomprise a separate and independent store, similar to a filesystem.However, the naming hierarchy is common across all modules, unlike atraditional filesystem, where a given name is bound to a logical device(filesystem). For example, if a traditional filesystem were mounted at/a/b/c, then all objects under that directory would be located in thatfilesystem. By contrast, the disk manager 206 is able to store/a/b/c/one.gif, /a/b/c/two.gif, and /a/b/c/three.gif in any of the cachedevices 803 a, 803 b, 803 c, it manages. During initial placement (aswell as relocation for load balancing), the disk manager 206 selects thedevice to store the object based on usage statistics it keeps on a perdevice basis. During lookup (to serve the STAT task), the disk manager206 determines which devices have the object and selects one, againbased on usage statistics. This allows objects, or portions thereof, tobe placed and served from any cache module independent of its name. Thedisk manager 206 is able to optimize the bandwidth from each device byplacing objects (and relocating them dynamically) based on usagestatistics. In an embodiment, the disk manager 206 keeps track of perdevice traffic in terms of read and write throughput for each device.During initial placement and relocation, it chooses the device with theleast amount of traffic. In another embodiment, it uses the queue depth(number of outstanding requests) and average latency as the measure oftraffic. The flexible placement results in linear scaling across cachedevices.

In an embodiment, the disk manager 206 caches the dictionary 804 a, 804b, 804 c, for each cache device 803 a, 803 b, 803 c, in RAM. Thedictionary 804 a, 804 b, 804 c, consists of the tree of objects storedin that device 803 a, 803 b, 803 c, along with a small amount ofmetadata about the object. This allows the disk manager 206 to answerthe STAT query very efficiently and without incurring any disk IO.

The disk manager 206 provides a simple fault recovery model. The failureof a single cache device just results in the loss of the objectscontained in that cache device. It has no impact on the performance ofthe other cache devices. The failed cache device can be replaced(online, for a hardware system that supports hot swapping) andreconfigured as a new cache module. In an embodiment, the disk manager206 can also selectively replicate objects in multiple cache devices inorder to get better fault recovery and performance.

In an embodiment, all information about videos is self-contained withineach drive such that drives can be moved between MFDs. Over time, diskmanager 206 queries the analytics module 802 to atomically move entiremovies or clips between drives and/or to inner or outer tracks in drivesin the SAS disks 803. Disk manager 206 provides data necessary for themedia manager 204 to promote and demote objects between various layerswithin the cache hierarchy. Initial placement of content can bedependent on data from the analytics module 802 and/or the policy module801. The disk manager 206 chooses the data layout that optimizes readperformance, even for small objects.

The disk manager 206 can avoid fragmentation problems that affectperformance for most filesystems. It does so by reclaiming entire blockswhenever a configurable amount of space has been freed in that block.For example, if a 2 MB block is filled with 64 objects of 32 KB each andhalf the objects are deleted, e.g., based on eviction, the disk manager206 can free the entire block. The RBM is used by the disk manager 206to logically delete or relocate the remaining objects.

Video information can include: compressed/uncompressed video data, videoattributes needed by an application (header information), and videoattributes needed to aid internal operation (cache expiry, cache initialtime). The disk manager 206 readjusts cache contents as drives areremoved and added. It also gracefully handles runtime errors from thephysical media. SAS, SATA, SSD, and flash drives are supported togetheron the same system. The disk manager 206 allows high levels ofparallelism to multiple drives. A possible embodiment allows pre-loadingof the cache with media which is can be served until a specific dateand/or time.

Intelligent Caching

Hard drives typically do not operate well as caches, when a hard driveis used as a cache and it is caching hundreds, thousands, or even tensof thousands of videos, the end result is a random input/output (IO)pattern. The MFD places interesting content in the same area of the harddrive so the MFD can perform large reads to compensate for bandwidth,e.g., for a low bandwidth connection, the MFD can read 30 seconds ofvideo in one read and store it in the cache in the RAM or SSD (orbuffered on the hard drive depending on the number of connections beingserved and bandwidth considerations of those connections). This allowsthe client to be served out of that cache and the client does not needits next IO for 30 seconds. The SSD is used for content that is accessedmore frequently or for content that requires smaller random IOs thatcannot be efficiently served from the hard drive. A popularity index isused for portions of content to determine whether a portion is hot. Forvideos, people may not be watching the entire video and some portions ofa video may be hotter than others, so the hottest portion of a contentis cached. This allows the MFD to be more intelligent in its caching.The MFD does not have to cache an entire video stream, for example. TheMFD dynamically computes the popularity of portions of content.

Referring to FIG. 3, the boundaries of the hot portions of video aredetermined dynamically as the MFD measures accesses of a video stream.In a possible embodiment, the server side player 201 uses a logicalchunking approach to dynamically determine where the hot portion of thevideo is. For example, the server side player 201 may use frameidentifiers such as time tags embedded in the video frames or storagememory address locations. The frame identifiers may be obtained by theserver side player 201 using a table of offsets created for the videostream. The table of offsets may be created by the system upon receiptof the video stream or created by a content provider which is loadedinto the system at the time the video stream is received. Multipletables may be stored for different bit rates of the video stream.

The server side player 201 can determine the portion or boundaries ofthe video stream that covers the most viewed frames of the video streamand places the hot portion of the video stream into one of the caches(hard drive, SSD, or RAM). In a possible embodiment, the analyticsmodule monitors video 1 301, video 2, 302, video 3, 303, and video 4404. It finds that there are sections of the videos that are viewed morefrequently than other parts of the videos or other videos by clientsystems. Those portions of the videos 305, 306, 307, 308, are stored inthe cache 309. The cache 309 may be any of the caches, RAM cache, SSDcache, or hard drive cache, or any combination thereof.

In a possible embodiment, the server side player 201 supports physicalchunking of a stored video stream that partitions the video stream intosmall files and determines which file is popular. Physical chunkingsplits the video into small named chunks that are visible to the clientplayer.

Time-based access patterns are used to determine which videos tend to bewatched together, e.g., subject-related news items or content-relatedvideos, and the disk manager 206 co-locates the hot portions of thevideos in the same area in the hard drive cache, SSD cache or RAM cache,thereby increasing cache hits and allowing for faster access times.

The RAM cache is integrated with the buffer manager 203. It usesanalytics and/or policies to manage the RAM cache and select evictioncandidates. As the server side player 201 finds each hot video portion,the buffer manager 203 determines which hot portions already stored inthe cache are no longer determined to be hot. The buffer manager 203removes portions that are no longer hot from the caches in order to makeroom for new hot portions. This is done by the buffer manager 203 basedon internal analytics derived from access patterns. In an embodiment,the buffer manager 203 keeps all buffers that are not in active useorganized by eviction order. The ordering takes into account factorslike the number of times the buffer was accessed, the time frequency ofaccesses, and the increasing/decreasing rate of use.

The buffer manager 203 can use main memory (RAM) as a cache for high-bitrate videos and SSD memory for low-bit rate videos. This allows the MFDto more efficiently use the main memory.

The media manager 204 manages the cache hierarchy (e.g., SSD, hard disk,peer). It looks at analytics and/or policies to determine when topromote, demote, or evict cache contents. The media manager 204initiates the hierarchical cache management which includes cachepromotion and demotion actions. The implementation for each element inthe cache hierarchy is called a cache provider. Providers aredynamically registered and assembled into a hierarchy based on theproperties that they register, e.g., bandwidth, latency, capacity, etc.There are two classes of providers: cache providers that are localcaches to the system that support reads and writes; and origin providersthat are networked sources that supply origin content and are read-only.The units of cache migration can incorporate the logical chunkboundaries or in some cases be purely derived from device level blockmanagement. For example, in the HDD, popular blocks (that may containportions of multiple videos) can be promoted to SSD or to the outertracks of the HDD.

Metadata describes where media is stored among the disks. Most operatingsystems cache information about files. The information is called aninode. An inode cache can hold many inodes, typically on the order ofmillions. This cache will consume precious memory which the MFD coulduse to cache media data. The MFD has information to tell it wherevarious pieces of media data are stored within the raw partition of adisk. This information falls under metadata and is called an “extent”.Each disk block which holds a large media object can have a singleextent to refer to that data. When a disk block holds multiple smallobjects, each small object has a separate extent to describe it.

In order to reduce the inode cache space which is hard to control insome systems, the metadata is packed, including extents, into singleinodes/files called containers. Each container holds the extents for aset of objects that are common. Because the objects are common the MFDwould have normally read the metadata for these objects.

In a possible embodiment, the MFD creates a dynamic disk hierarchy thatallows the MFD to determine the bandwidth of the disks within the MFD.The disk manager 206 determines which drives are possible cache targets.It runs a short test to categorize each drive according to diskbandwidth. This is done because the same type of drive can see differentperformance numbers depending on which disk controller is in front ofit. By running a disk test, the disk manager 206 does not need todistinguish between various drive types or figure out what performanceeach disk controller can deliver. The drive/controller bandwidthcombination will place the pair within some category set by the factoryor by an administrator. There typically are a preset number ofcategories.

In a possible embodiment, the MFD creates a disk cache hierarchy. Eachlevel of the cache hierarchy contains a set of objects. Objects near thetop in terms of number of accesses are good candidates to move into thenext fastest hierarchy, thereby enabling a decrease in total access timefor all objects. Movement of an object from a lower level to a higherlevel can be determined using the bandwidth usage and the space usage todetermine when it is appropriate to move the object. Objects near thebottom in terms of number of accesses are good candidates to move intothe next slowest hierarchy, freeing up room for higher access countobjects. The MFD attempts to maximize the available bandwidth for thehighest level to the lowest level. For example, three levels, A, B, andC, are defined, with A being the fastest cache. If A is not full, thenit would make sense to promote the highest accessed objects in B to A.This would leave more room to promote objects from C to B. If someobjects in B are accessed less frequently than objects in C, then itwould make sense to demote the least accessed objects in B by movingthem from B into C and the promote the most accessed objects of C intoB. This movement process is called “promotion” and “demotion”.

The outer 10-15% of each disk drive can deliver 15-20% betterperformance than the random performance of an entire drive. A possibleembodiment can carve out the outer part of a drive and migrate thehottest parts of media objects to this area.

Buffer Manager 203

The buffer manager 203 provides the primary data path within the MFD.All content served by the MFD are sent via buffers. Buffers are usedboth for speed matching (buffering) between the outbound network and thecache providers as well as a RAM cache. The latter is the (implicit)first level in the cache hierarchy. When requested content is notavailable in the cache, the buffer manager 203 uses the services of themedia manager 204 to retrieve that data and cache it for subsequentrequests if possible.

The buffer manager 203 receives a request for content from a task thatthe HPE creates. The buffer manager 203 fetches content. Given a URL andan offset to play from, it will supply the content. The buffer manager203 retrieves the content from media manager 204. The buffer manager 204creates a task to retrieve a portion of the video content starting atthe offset. The media manger 204 retrieves the content form the harddrive or SSD. The buffer manager 203 can check if the requested contentmatches any content stored in the main memory cache (RAM). The RAM cacheis composed of a plurality of buffers. A hit can be directly served fromthe cache without any further copying. A miss is served by filling a newbuffer using the media manager 204 to locate the content in storage. Thebuffer manager 203 passes a pointer to the buffer containing the portionof video content to the output protocol engine 210 which streams theportion of video content to a client.

The buffer manager 203 efficiently manages a large amount of memory. Ithas the ability to share buffers across connections that are serving thesame content. The buffer manager 203 also has an efficient re-use schemederived from the usage pattern in the MFD.

The buffer manager 203 handles buffer eviction based on a cost functionthat is calculated based on the use count and age. A higher use countresults in a higher cost, whereas the age acts as a decay function onthe cost, e.g., older buffers have a lower cost. The eviction algorithmattempts to approximate finding the lowest cost buffer while operatingvery efficiently (constant time).

A buffer that can be evicted (has a zero reference count) is inserted atthe tail of an LRU list. The lists are ordered by the use count of thebuffers. Each LRU list is effectively ordered by timestamp. A bufferthat is not in the cache (e.g. expired, purged) is put on the head ofthe lowest LRU list with a zero timestamp.

During the eviction, the cost is computed for the head of each LRU listand the lowest cost buffer is evicted.

Each object (URI) has an expiry time that is part of the attributes. Onaccess in the buffer cache, the expiry time is checked against thecurrent time. If expired, all the buffers and the attributes associatedwith the object are removed from the cache. The buffers are put on theLRU lists when the reference count becomes zero. An object can berevalidated with the origin server during a time window (that can beconfigured by the administrator or user) prior to the expiry time.

Referring to FIG. 9, in a possible embodiment, the buffer manager 203manages the buffer pool 904. The memory available for data is staticallydivided into an array of fixed size pages. Each page has a correspondingbuffer structure to encapsulate the metadata associated with a buffer.The buffer structures are also statically allocated from an array. Eachbuffer can be linked via the buffer cache and the free list. Some of theelements of the metadata are:

-   -   Identity. The identity of the buffer. Data buffers have an ID        consisting of the UOL (URI, Offset and Length). Attribute        buffers have an ID of URI only.    -   Reference Count. The number of active users of the buffer.    -   Use Count. The number of times the buffer has been used. This is        the basic measure of the buffers “popularity”.    -   Timestamp. The time at which the buffer is put on the LRU list        (i.e. reference count is zero).

The buffer manager 203 manages the buffer cache. A hash map using theUOL as the key is maintained for all buffers that have an identity andcan be shared with other connections. A possible embodiment supports anon-cached mode for a buffer whereby it has an identity, but is notshareable.

Data buffers associated with the same object (URI) are linked togetherwith a list rooted in the corresponding attribute buffer. This allowsfast application of actions that pertain to the entire object (e.g.,cache expiry and object purge).

A free list is also maintained by the buffer manager 203. All buffers,including those with an identity, that have a zero reference count areon this list. This allows for efficient eviction of buffers as needed.The list can be composed of multiple lists ordered by the use count ofthe buffers.

Each GET task allocates some private data in the cache request privatedata 905 that is used to keep a list of its buffers for referencecounting. It is also used to link to an underlying media request. Thecache request handler 902 manages the cache request private data 905 andhandles the GET task requests.

The media request handler 903 captures the in/out arguments for eachmedia GET task sent to the media manager 204. Media Request objects arelinked into a media request table 906 so that multiple requests to thesame, or co-stored, objects can be synchronized.

Referring to FIG. 10 a, the interface between buffer manager 203 and themedia manager 204 (which implements the cache hierarchy) has uniquecharacteristics that enable the high performance caching system. Theselection of the device that provides the data is done using a STAT taskthat acts like a bidding system. Each layer in the cache hierarchy,e.g., solid state device (SSD) manager 205, disk manager 206, and originmanager 207, can respond, in turn, to bid for serving the request. Thebid includes a “blocksize” that tells buffer manager 203 to allocate therequisite set of buffers. The buffer manager 203 then sends down a GETrequest to the specific cache provider that won the bid. The request andresponse are logically decoupled. The provider fills the suppliedbuffers with content and sets the appropriate identity for each buffer.This results in the new buffers being inserted into the RAM cache. Uponcompletion of the task, buffer manager 203 looks up the RAM cache againand is able to find the buffers it was looking for. This model allowsthe providers to supply additional data, either subsequent portions ofthe same object or other related objects, in the same request. It alsoallows various portions of an object to be supplied by differentproviders. Naming and location are orthogonal. For example, a videoobject with a name /a/b/c/one.flv can exist (in parts or whole) in anyof providers in the cache hierarchy.

Media Manager 204

The media manager 204 promotes and demotes videos based on the relativehotness of the video. The hotness of the video is a function of thenumber of hits on that video, the frequency of hits, and the increasingor decreasing trend of the frequency.

The media manager 204 has n different sources, the SSD(s) 205, harddisk(s) 206, origin server 207, or peer 208. It receives a buffer andfills it with a portion of the requested content. The media manager 204sends the filled buffer to the buffer manager 203. If the content is notin local storage the media manager 204 retrieves the content from theorigin server, a peer, or a client. The following is the hierarchy ofspeeds, in a possible embodiment, associated with each source:

1. Memory (RAM): 10 Gbps

2. Flash: 4 Gbps

3. Solid State Device (SSD): 1.6 Gbps

4. Disk (SAS): 550 Mbps

5. Disk (SATA)—400 Mbps

6. Others

7. NFS and other file caches.

8. Origin Manager.

Referring to FIG. 10 b, the media manager 204 first places a new videoin the lowest memory hierarchy. On a timer expiry, the media manager 204checks the analytics/policies manager 1002 for the hottest and thecoldest video. The analytics/policies manager 1002 provides the mediamanager 204 with the hottest videos and/or portions of videos accessed.The hottest video or portion of video is promoted to the next memorycache in the hierarchy and the coldest one is demoted to the next lowestin the hierarchy. In this way, a video can be placed in the lowest tierof a cache hierarchy and can bubble to the top of the hierarchy if itshotness increases relative to other videos.

The media manager 204 drives the eviction of videos from the respectivecaches. It implements an eviction timer. When the timer fires, the mediamanager 204 goes through each cache provider 205, 206, 207, 1006,checking whether the cache is full to a certain threshold. If aparticular cache is full, the media manager 204 calls the evictionfunctionality of the provider. The provider then performs its specificalgorithms for eviction.

Peer Manager 207

The peer manager 207 can be configured to obtain certain content from apeer MFD upon a cache miss. Given that a MFD has a limited amount ofstorage space in local storage such as one or more hard drives and oneor more SSDs, a scenario may exist where a customer has more videocontent than a single MFD can store. The customer's video content can bedistributed among a plurality of peer MFDs installed at the customer'ssite or, where the peer MFDs are accessible to each other over a networksuch as an intranet, Internet, LAN, or WAN, distributed among theplurality of peer MFDs that are in communication with each other.

An administrator can inform each peer MFD of the IP addresses of itspeers so a peer MFD is able to communicate with its peers. If the peerMFDs are locally attached, they can discover their peers by themselvesthrough any type of discovery mechanism. The peer MFDs can communicateamong themselves and let each peer MFD know what URLs it caches. Thismeans that after each peer MFD has loaded content from an origin serveror another peer MFD, it informs each of its peer MFDs about the URLsthat it serves. This can be via a message or series of messages sent toeach peer MFD or broadcasted to all peer MFDs. If a request for aspecific URL is sent to a peer MFD that causes a cache miss, the peermgr in that MFD can request the URL content from a peer MFD that cachesthat specific URL.

Origin Manager 208

The origin server may push content to the origin manager 208 or theorigin manager 208 may pull content from the origin server. The originserver may push content to the origin manager 208 by pre-staging thecontent to the origin manager 208. The origin server can FTP or HTTPinto the origin manager 208 and tell the origin manager 208 to cachecertain URLs because the content provider knows that the content will behot.

The origin manager 208 pulls content from the origin server as a resultof a client request that misses all locally available caches (also aproxy function). Pulling content can also occur due to a policy orcommand driven action to fetch content separately from a client request.The proxy function is separate from the cache ingestion. There areseveral reasons for this: (a) the proxy may have to serve oddly alignedbyte range requests that are not convenient for caching; (b) the systemmay need to perform processing functions like chunking and transcodingduring ingest (these are difficult to do in real time in the proxy); and(c) different policies for the two functions.

Input Protocol Engine 209

The input protocol engine 209 operates in the same manner as the outputprotocol engine 210, except that it communicates with origin serversusing protocols such as HTTP, FTP or NFS.

Optimized Network Stack 211

The optimized network stack 211 uses the round trip time (RTT) in theTCP stack to estimate the last mile bit rate variation to the client.The RTT time tells the optimized network stack 211 if there iscongestion down the line. The RTT provides an estimate of bandwidthavailable in the network going to the client. The optimized networkstack 211 also implements error handling and congestion control usingalgorithms suitable for time sensitive applications such as video. TheMFD can change the bit rate in response to the detected bit rate changeswithout the client knowing.

Assured Flow Rate

In a possible embodiment, the MFD has the ability to guarantee a certainclass of service to every flow admitted into the system for datadelivery. This is called the assured flow rate. The MFD calculates theassured flow rate for each session and sets up a maximum bandwidth forthe session. The bandwidth usage for the session should be no less thanthe assured flow rate and should attempt to reach maximum bandwidth ifthere is bandwidth available.

The MFD implements flow control to ensure that existing sessions get therequired rate and no more than the maximum. This is achieved in thenetwork socket level. The socket level manages the data send rate. Thesession bandwidth queue and server timer are used for calculating flowcontrol.

The MFD performs admission control and connection management by ensuringthat a new session is not admitted if the server does not have enoughresources to accept the connection.

Four metrics can be used for the MFD to maintain the assured flow rate(AFR):

ΣAFR of all connections≦Appliance Interface port Bandwidth

Session AFR≦Client Session Bandwidth

ΣAFR of all connections≦(Disk+Buffer) Read speed

Poorest Quality video bit rate≦Session AFR≦Highest Quality video bitrate

Where:

-   -   Session: A single TCP connection.    -   ΣAFR of all connections: Sum of AFR of all accepted sessions.    -   Session AFR: Individual AFR for one single session.    -   Client Session Bandwidth: The client session maximum bandwidth.        Typically the client session maximum bandwidth refers to the max        TCP throughput due to the limitation of the WAN environment. For        a DSL download, the typical bandwidth is 1,500 Kbits/sec.    -   Video bit rate: Each video has a profile. Different profiles        have a different quality. Higher quality videos require a higher        bit rate. Not every video has a profile for all bit rates. A        typical video profile bit rate could range from 200 Kbits/sec to        1,000 Kbits/sec.

To ensure that the MFD does not over commit server resources so that theAFR for existing sessions can be maintained, the MFD either rejects anew session or lowers the profile (if possible) for existing sessions toaccommodate the new session based on a policy setting. A session isrejected by sending over a server busy HTTP reply or by simply closingthe connection. The MFD does not close sessions in the middle of servingdata. It simply lowers the video profile.

For example, if the total appliance network bandwidth is limited to 1Gbits/sec for each network interface port, then the ΣAFR of all sessionsshould be less than this bandwidth. When the sum of the AFR of all ofthe accepted sessions is equal to 1 Gbits/sec, the MFD can stopaccepting new sessions. In a possible embodiment, by considering thenetwork overhead used by packet retransmission, ACK packet, TCP/IPheader, other usages such as ARP, the offline origin manager 208, etc.,the bandwidth can be reduced to 0.8 Gbits/sec for all session AFRcalculations in order to take in to account a more realistic bandwidthlimitation.

The AFR bit rate can be between the poorest quality video bit rate andhighest quality video bit rate. If the AFR<poorest quality video bitrate, then screen jitter will occur at the client side. If theAFR>highest quality video bit rate, then bandwidth resources are beingwasted. The server side player 201 does not close a continuous sessionGET request but is allowed to close a new session by returning a failureerror code.

In a possible embodiment, if a client is gaining access via a dial-inmodem, the AFR is limited by this slow last mile connection. The networkdriver module detects the client connection ISP speed based on RTTcalculation. An example equation can be: client session bandwidthspeed=1460 bytes/RTT in seconds.

As discussed above, video content is stored in the disk or RAM. Once theMFD determines the AFR, it needs to make sure that the disk+buffer canachieve this speed. Disk speed, as a capacity, is not something that iseasy to measure, unlike CPU and network capacity. It is highly workloaddependent. A more practical way to measure if the disk is at or close tocapacity is to look at queue depth and/or average latency. Thescheduler's 202 deadline miss counter is a good indicator of what ishappening in the system.

Under certain situations, for example, the Web master wants to create aVIP list. The Web master through the user interface management consolemay set up a policy so that the VIP list receives high quality videowhich results in a higher AFR for the session. In another example, theWeb master can set an average video quality. The Web master can use theuser interface manager console to set an average AFR.

In a possible embodiment, the MFD does not want to send a higher videoquality to a client that cannot play the high quality video. Forexample, a PC/Laptop can play high quality videos, but aniPhone/g-phone/Palm, etc., only has very small screen and thereforecannot play a high quality video. It is completely unnecessary to sendover high quality videos to these kinds of devices.

Referring to FIG. 11, a data flow is shown for a possible embodiment ofthe AFR portion of the network manager in the optimized network stack211 sending data out after the HPE posted a task to the scheduler 202and the scheduler 202 returned a chunk of data. If the calculated sizeof data cannot be sent out within one timer interval slot (e.g., once asecond), it means an AFR miss occurred in the network manager. Ifscheduler 202 does not return a task within a deadline miss time, itmeans an AFR miss in the disk manager 206.

The network manager calculates the deadline time for the task. It thenposts a task with the calculated deadline time 1101. The network managerthen calculates the maximum number of bits that can be sent over theconnection given the AFR and the timer interval for the transmissionperiod for the socket. This results in the maximum amount of data thatcan be sent over the connection in one timer interval 1102. The networkmanager then sends the data over the socket 1103.

If the send was incomplete 1104, e.g., there was not enough space forthe data to be sent or the timer interval has lapsed, then the networkmanager attempts to resend the data over the connection 1107, 1103.

If there was enough space for the data to be sent out/received 1104(e.g., the buffer level on the client was sufficient, the TCP level wassufficient, the window size was sufficient, more data is to be sent,etc.), then the network manager checks to see if there is more data tosend 1105. If more data is available to send, then the network managerputs the socket back into the timer queue to wait for the next timerinterval to send more data 1108 and calculates the next maximum numberof bits that can be sent over the connection 1102. Otherwise, thenetwork manager is finished with the timer interval and gets the nextchunk of data to send 1106.

The process continues until all data from the chunk(s) of data from thescheduler 202 has been sent.

In a possible embodiment, the MFD performs the following in order tomaintain the AFR:

1. Connection requested on a network port. If this network port's totalconnections>max allowed connections, reject the connection.

2. Each connection can only share up to the calculated sessionbandwidth. In this example=1 Gbps/total connections on this networkport.

3. Modification due to maximum session bandwidth configuration.

-   -   a. If maximum configured session bandwidth is configured and the        calculated session bandwidth>maximum session bandwidth, set the        calculated session bandwidth to maximum configured session        bandwidth.    -   b. Else make no change.

4. Calculate session AFR.

-   -   a. Set session AFR to configured AFR as base suggested AFR.    -   b. Call server side player 201 for adjusting the AFR. If error        message is returned by server side player 201, close session.

5. Modification due to balanced AFR calculation.

-   -   a. If calculated session bandwidth>1.2*AFR, set the calculated        session bandwidth to 1.2*AFR.    -   b. Else make no change.

6. Modification due to AFR.

-   -   a. If the calculated session bandwidth<AFR, set the calculated        session bandwidth to AFR.    -   b. Else make no change.

7. The calculated session bandwidth is enforced in every epollout eventor task completion, on whenever data is about to be sent out to theclient.

The network and HTTP manager provide three parameters to the server sideplayer 201 for calculating the server side player 201 AFR value. Thethree parameters are:

URI.

Client Session Bandwidth (Ceiling value of AFR).

Total available AFR of network bandwidth.

Where:

-   -   Total available AFR may be trimmed by network module.    -   Total available AFR≠Total network bandwidth−ΣAFR of existing        sessions.    -   Total available AFR=min (Total network bandwidth−ΣAFR of        existing sessions, configured maximum AFR)

In the server side player 201 AFR calculation, the return AFR value canbe less than client session bandwidth and total available AFR. Theserver side player 201 can be called at the time after the HPE finishesHTTP parsing. The HPE provides all HTTP information (such as URI, etc.)as well as a flag to show this is a new session or a continuing sessionwith the same connection.

The server side player 201 does not close a continuing session GETrequest but should be allowed to close a new session. The server sideplayer 201 sets the AFR to the value specified in the URI request. Ifthe server side player 201 is unable to set the AFR to the requestedvalue, it returns an error code to the HTTP Engine that will close theconnection.

The scheduler 202 deadline misses can be used to measure disk throughputduring runtime. The HPE calculates the deadline (usingdeadline=func(total HTTP bytes/AFR)) in microseconds and sends thedeadline to the scheduler 202 when submitting a task to the scheduler202. If a disk operation is over loaded, then the scheduler 202 dropssome new tasks. The selected dropped tasks should belong to the firsttasks created by a new session. A flag can be set by the HPE to tell thescheduler 202 if a task belongs to a new session or not.

When there are too many disk deadline misses, the scheduler 202 sendsfeedback to the network manager to reduce the maximum allowedconnections in the server structure. This reduces the total sessionnumber.

After a disk operation is recovered and the deadline miss issue ispassed over, the scheduler 202 tries to recover back to the maximumallowed connections setting in the server structure.

Hint Tracks

Referring to FIG. 12, in a possible embodiment, a progressive downloadhint track (PDH) 1206 describes to a MFD how to serve media dataresiding in a file 1201 using progressive download over HTTP. Only onecontainer file 1201 needs to reside in the MFD. Within this containerfile 1201 a user could store streams 1204, 1205, of varying bit-rates,spatial resolutions or scalable streams. The container file 1201 canalso contain metadata 1202 as with MP4 container files. The PDH-Hinttrack 1206 would be a higher level meta box within the video filecontainer (moov in this example) 1203 that describes to the MFD all theoptions available to it to support PDH.

In a possible embodiment, depending on requests from the client to adaptto varying bandwidth conditions, available client CPU resources, or bythe MFD polling the network to account for network latency, the MFD sidelogic can make intelligent decisions as to how and what kind of bitrate, frame rate, or resolutions it should serve to best meet theconditions of the network and the requirements of the client.

In a possible embodiment, the hint track can be used by the MFD todecide the best rate or resolution to serve and then encapsulate therelevant portion of the time period of media data as a selfcontainerized chunk of MP4 to deliver over HTTP. The media data itselfthat resides in the generic container does not need to be reformatted inany way.

In a possible embodiment, multiple predefined PDH hint tracks could becreated that cover most of the common usage conditions to reduce theload on the MFD side.

In a possible embodiment, a single stream of media data can be used in aserver composed to serve at a predefined frame rate (e.g., an H.264stream coded at B₁ kbps at 30 fps). During delivery, depending onnetwork conditions, the MFD can choose to drop the higher temporalenhancement layers (information for which can be easily obtained by thelayering boxes in MP4). As such, the rate of the PDH chunk for theselower frame rate portions (e.g., 15 fps, 7.5 fps) would be less than B₁kbps thereby providing a mechanism to quickly adapt to bandwidthfluctuations while not affecting the playback quality experience of theuser to a large extent.

In a possible embodiment, an additional hint track (or higher level box)can be used to describe to various options available to supporttrickplay. Such a hint track (or box) can provide information to the MFDabout the speed of fast-forward or rewind (2×/4×/−2×/−4×, etc.) alongwith precise information about relative frame offsets and playback ratethat will aid the client player during playback.

In a possible embodiment, the hint track usage could also be extended tosupport MFD side playlists. These hint tracks can provide informationabout where ads or video segments need to be inserted and their exactdurations. The hint tracks can also provide control mechanisminformation, for example, if a client player can skip or fast-forwardthrough an ad or video segment. The hint tracks may also containinformation about which ad server to contact, if needed, for the dynamicplacement of ads or video segments.

MFD Policies

An administrator is able to set policies for the MFD to operate upon.For example, the administrator may desire to have the MFD serve as manyclients as possible or serve HD content and retain the quality of the HDcontent at the cost of serving a large number of clients.

The feedback from the scheduler 202 as to the amount of time that taskshave been late, the number of tasks that have been late, or any otheruseful metric, can be sent to the server side 201 and/or the outputprotocol engine 210. The server side 201 can use the information toadjust the number of clients that it is serving or even adjust thequality of the video that it delivers to certain clients in order toresolve the delivery latency. It may be that certain clients running atcertain bandwidths are flexible enough to have their bandwidthdynamically lowered.

The output protocol engine 210 can use the information from thescheduler 202 to deny any new client connections until the scheduler 202passes the output protocol engine 210 statistics that show that the MFDhas caught up sufficiently with the desired delivery efficiency. Theparameters defining what criteria are used to make such a determinationmay be defined by an administrator. Such parameters may includeperforming an action based on the number of clients that are beingaffected by late deliveries or the amount of latency that exists, e.g.,the number of tasks that are missing deadlines.

An administrator may configure the origin server to notify the MFD aboutwhich content servers it should communicate with in order to retrievecontent when the MFD experiences a cache miss. The origin server caninstruct the origin manager 207 to obtain certain content from aspecific content server using a specific protocol. The origin server canalso define policies on the MFD to tell the origin manager 207 whichcontent is cacheable and which content must be obtained from an originserver, e.g., seldom requested content.

MFD Extensions

The MFD may also be bandwidth limited at the factory. The MFD may be setto not exceed a certain peak bandwidth or number of open sessions. Thisallows the MFD provider to sell certain levels of service. If a customerrequires a higher peak bandwidth or more open sessions, the MFD providercan remotely set the peak bandwidth or maximum number of open sessionsof the customer's MFD remotely for a fee that may be a one-time fee or arecurring fee. The MFD may also automatically exceed the maximumbandwidth or maximum number of open sessions and notify the MFD providerof the amount exceeded. The MFD provider may then charge the customer afee for the exceeded amount. This allows the customer to temporarilyhandle high activity bursts and not have to purchase an additional MFDor a MFD upgrade.

Load Balancer Interaction

There typically is a load balancer in communication with the peer MFDs.The load balancer can be configured to send a client request to acertain peer MFD when the request is for a specific URL. One of the peerMFDs may a send a table of what URL is available for each peer MFD.Alternatively, each peer MFD can tell the load balancer what URLs itserves. The load balancer can gather all of the information from thepeer MFDs and create its own tables or database entries in order todirect client URL requests to the correct peer MFD. The load balancermay use a hashing scheme based on the URL and/or other parameters todetermine the MFD to direct a URL request to. This allows the URLcontent to be distributed among the peer MFDs.

Monitoring and Statistical User Interface

An administrator, or the like, can look at the MFD's stored statisticsthat the server side player 201 records and can see via textual orgraphical representations how the MFD is performing. The media manager204 also records the number of cache hits and misses as well as whatcontent is the most popular (hot content) or least popular. The mediamanager 204 can also record the origin servers that it has requestedcontent from and the number of times such requests were made. The userinterface allows the administrator to observe the content performancedata in a graphical or textual representation. The user interface canpresent any recorded information for a specified period of time or inreal time.

A graphical user interface allows the MFD to use statistical informationthat it can collect with regard to disk use and content accesses todisplay graphical charts that visually represent any of:

-   -   Histogram data showing recent data retrieval times per disk.    -   Disk access counters.    -   Number of videos per disk.    -   Amount of free space.    -   Number of videos requested.    -   Number of videos requested per disk.    -   Recent throughput per disk.    -   Hits/misses in the buffer cache.    -   Various buffer operations.    -   Errors (from media manager statistics, media request, etc).    -   Number of videos stored.    -   Number of videos per cache.    -   Number of videos created.    -   Number of videos deleted.    -   Number of media providers.    -   Meta-information about media providers.    -   Bandwidth served per cache level (memory, SSD, Disk) as well as        Origin sources (HTTP, NFS, etc.).    -   Bandwidth served per cache device (each SSD or Disk unit). The        caching logic is designed to load level across devices as the        workload profile changes with respect to content.    -   Bandwidth and connections served per interface port.    -   Bandwidth and connections served per protocol (HTTP, RTSP, etc).

In a possible embodiment, a user may configure parameters relating tothe performance characteristics of the MFD. Components such as theserver side player and media manager record performance statistics thatare used by the graphical user interface to display statistics andgraphs to the user. FIG. 13 shows a user interface screen in a possibleembodiment where the user can specify parameters such as the AFR 1304 orthe maximum bit rate per session 1305. The user can also specify anamespace 1301 along with its URI 1302 and the host name of the HTTPorigin server 1303 for the namespace.

Referring to FIG. 14, in a possible embodiment, a graphical userinterface screen 1400 can show a real time graph of the aggregate numberof bytes 1401 transferred from the cache, origin server, and totaloverall bytes delivered to clients over time 1402. The graphical userinterface screen 1400 allows the user to see the actual performance ofthe MFD as it delivers content to clients 1403. The user can customizethe policies in the MFD to adjust for cache storage, for example, tohandle certain hot content that the user always wants available. Thegraphical user interface 1400 immediately shows the user the affect thathis changes have on the MFD.

FIG. 15 shows a screenshot 1500 of the graphical user interfacedisplaying the performance characteristics over the MFD's connections1501.

3.2 Media Flow Director Placement

FIG. 4 illustrates a possible embodiment using MFD's 401 to replaceexisting video servers 402. Existing video server implementations aretypically a group of file servers 403 that cache content from an originserver or a group of origin servers 404. The content from the originservers 404 are mirrored across many video servers 403. A user, via aclient, visits a web page on a portal server 405 to search for videocontent. The user selects a video from the web page via a link on thepage. The URL is sent to a DNS server that resolves the URL to an IPaddress that a load balancer is responsible for. The client is passedthe resolved IP address which is used by the client to make the videorequest. A router, in a group of edge routers 407, routes the request tothe load balancer in a distribution center 406. The load balancerreceives the request and forwards the URL request to a video server inthe video server cluster 402. The URL request may inform the videoserver the bit rate of the requested video that the client is expecting.The video server is a file server that has no knowledge of thecharacteristics of the file that it is delivering other than the factthat it must deliver a certain bit rate version of the video to aclient. Typically the name and content is opaque to the video server.Each bit rate of the video is typically a named file. The video serverstreams the video file to the client and attempts to deliver the videoto the client such that the client's video buffer does not become empty.

The client must buffer the received video in order to cover for delaysin the streaming of the video from the video server. The client's bufferis meant to give the user a continuous viewing experience. Given thatthe video servers are serving large amounts of videos to many clients,delivery delays that are created by a server running out of bandwidth orby network delays to a client are frequent and client buffers becomeempty. As a result, the user either sees the video stream stop playinguntil the buffer starts to fill again or, for small video files, waitsuntil the entire video has loaded into the buffer before the videostarts to play.

In a possible embodiment, one MFD has the ability to achieve athroughput of 10 Gbps+ resulting in a single MFD replacing ten or morevideo servers. Two MFDs 401 can replace a bank of 20 video servers. TheMFDs 401 communicate with origin servers 402 in order to obtain videocontent when a MFD receives a request for URL content that the MFD doesnot have in storage or the when MFD accepts new video content from anorigin server. The MFDs are a direct replacement of video servers andthe infrastructure of the portal servers 405, edge routers 407, anddistribution switches 406 remains the same.

FIG. 5 illustrates the placement of MFDs at edge and/or originlocations. In this example, the dashed lines are the data paths for aconventional implementation. A MFD may be installed at a content owner'ssite 501, a CDN 502, 506, a content aggregator site 504, or an ISP. Anycombination of locations may have a MFD installed. resulting in fasterand more reliable content delivery to clients 508. For example, when twoMFDs are installed at an ISP 507, the MFDs are deployed somewhere in theISP network. This can be either in the same data center in a cluster orin different data centers but in the same ISP access network. The MFDscan communicate with each other to deliver the content more efficientlybecause, if the MFDs can retrieve the content from within the samenetwork, it is more efficient than retrieving the content from acrossdifferent and/or multiple different networks or from an origin site. Ifa large content aggregator 504 deploys an all-MFD private deliverynetwork, the content aggregator sees even more efficiency since the MFDscan use private protocols to processes cache miss processing,pre-staging, data collection, etc., even more efficiently.

When an all-MFD implementation is achieved, there is a dramatic increasein efficiency due to the MFD's ability to retrieve content via the mostefficient route.

Note that the term “video content” has been used in embodimentdescriptions throughout the text. The term “video content” may bereplaced by any media type in the embodiments discussed throughout asthe MFD is adaptable to deliver any type of content files, such as:media (audio, pictures, etc.), games, software, HTML, scripts, etc.

4.0 IMPLEMENTATION MECHANISMS Hardware Overview

FIG. 6 is a block diagram that illustrates a computer system 600 uponwhich an embodiment of the invention may be implemented. Computer system600 includes a bus 602 or other communication mechanism forcommunicating information, and a processor 604 coupled with bus 602 forprocessing information. Computer system 600 also includes a main memory606, such as a random access memory (RAM) or other dynamic storagedevice, coupled to bus 602 for storing information and instructions tobe executed by processor 604. Main memory 606 also may be used forstoring temporary variables or other intermediate information duringexecution of instructions to be executed by processor 604. Computersystem 600 further includes a read only memory (ROM) 608 or other staticstorage device coupled to bus 602 for storing static information andinstructions for processor 604. A storage device 610, such as a magneticdisk or optical disk, is provided and coupled to bus 602 for storinginformation and instructions.

Computer system 600 may be coupled via bus 602 to a display 612, such asa cathode ray tube (CRT), for displaying information to a computer user.An input device 614, including alphanumeric and other keys, is coupledto bus 602 for communicating information and command selections toprocessor 604. Another type of user input device is cursor control 616,such as a mouse, a trackball, or cursor direction keys for communicatingdirection information and command selections to processor 604 and forcontrolling cursor movement on display 612. This input device typicallyhas two degrees of freedom in two axes, a first axis (e.g., x) and asecond axis (e.g., y), that allows the device to specify positions in aplane.

The invention is related to the use of computer system 600 forimplementing the techniques described herein. According to oneembodiment of the invention, those techniques are performed by computersystem 600 in response to processor 604 executing one or more sequencesof one or more instructions contained in main memory 606. Suchinstructions may be read into main memory 606 from anothermachine-readable medium, such as storage device 610. Execution of thesequences of instructions contained in main memory 606 causes processor604 to perform the process steps described herein. In alternativeembodiments, hard-wired circuitry may be used in place of or incombination with software instructions to implement the invention. Thus,embodiments of the invention are not limited to any specific combinationof hardware circuitry and software.

The term “machine-readable medium” as used herein refers to any mediumthat participates in providing data that causes a machine to operationin a specific fashion. In an embodiment implemented using computersystem 600, various machine-readable media are involved, for example, inproviding instructions to processor 604 for execution. Such a medium maytake many forms, including but not limited to storage media andtransmission media. Storage media includes both non-volatile media andvolatile media. Non-volatile media includes, for example, optical ormagnetic disks, such as storage device 610. Volatile media includesdynamic memory, such as main memory 606. Transmission media includescoaxial cables, copper wire and fiber optics, including the wires thatcomprise bus 602. Transmission media can also take the form of acousticor light waves, such as those generated during radiowave and infra-reddata communications. All such media must be tangible to enable theinstructions carried by the media to be detected by a physical mechanismthat reads the instructions into a machine.

Common forms of machine-readable media include, for example, a floppydisk, a flexible disk, hard disk, magnetic tape, or any other magneticmedium, a CD-ROM, any other optical medium, punchcards, papertape, anyother physical medium with patterns of holes, a RAM, a PROM, and EPROM,a FLASH-EPROM, any other memory chip or cartridge, or any other mediumfrom which a computer can read.

Various forms of machine-readable media may be involved in carrying oneor more sequences of one or more instructions to processor 604 forexecution. For example, the instructions may initially be carried on amagnetic disk of a remote computer. The remote computer can load theinstructions into its dynamic memory and send the instructions over atelephone line using a modem. A modem local to computer system 600 canreceive the data on the telephone line and use an infra-red transmitterto convert the data to an infra-red signal. An infra-red detector canreceive the data carried in the infra-red signal and appropriatecircuitry can place the data on bus 602. Bus 602 carries the data tomain memory 606, from which processor 604 retrieves and executes theinstructions. The instructions received by main memory 606 mayoptionally be stored on storage device 610 either before or afterexecution by processor 604.

Computer system 600 also includes a communication interface 618 coupledto bus 602. Communication interface 618 provides a two-way datacommunication coupling to a network link 620 that is connected to alocal network 622. For example, communication interface 618 may be anintegrated services digital network (ISDN) card or a modem to provide adata communication connection to a corresponding type of telephone line.As another example, communication interface 618 may be a local areanetwork (LAN) card to provide a data communication connection to acompatible LAN. Wireless links may also be implemented. In any suchimplementation, communication interface 618 sends and receiveselectrical, electromagnetic or optical signals that carry digital datastreams representing various types of information.

Network link 620 typically provides data communication through one ormore networks to other data devices. For example, network link 620 mayprovide a connection through local network 622 to a host computer 624 orto data equipment operated by an Internet Service Provider (ISP) 626.ISP 626 in turn provides data communication services through the worldwide packet data communication network now commonly referred to as the“Internet” 628. Local network 622 and Internet 628 both use electrical,electromagnetic or optical signals that carry digital data streams.

Computer system 600 can send messages and receive data, includingprogram code, through the network(s), network link 620 and communicationinterface 618. In the Internet example, a server 630 might transmit arequested code for an application program through Internet 628, ISP 626,local network 622 and communication interface 618.

The received code may be executed by processor 604 as it is received,and/or stored in storage device 610, or other non-volatile storage forlater execution.

5.0 EXAMPLES

In an embodiment, an apparatus comprises: a media delivery requestreceiver that receives requests for media content from client systems, aflow rate subsystem that calculates a maximum bandwidth and a targetflow rate for each outbound media flow, a delivery subsystem that, foreach outbound media flow, delivers at least a portion of a requestedmedia content to a client system, a media delivery scheduling subsystemthat determines when the delivery subsystem delivers at least a portionof a requested media content, the media delivery scheduling subsystemdynamically adjusts flow rate for each outbound media flow in order tomeet the target flow rate for each outbound media flow, the mediadelivery scheduling subsystem instructs the media delivery requestsubsystem to refuse incoming media requests when the media deliveryscheduling subsystem detects that target flow rates for media flows maynot be achieved if additional media content requests are accepted.

In an embodiment, an apparatus further comprises wherein the mediadelivery scheduling subsystem instructs the delivery subsystem todeliver at least a portion of a lower quality media content in order tomeet the target flow rate for a specific media flow.

In an embodiment, an apparatus further comprises wherein the mediadelivery scheduling subsystem instructs the delivery subsystem todeliver at least a portion of a higher quality media content in order tomeet the target flow rate for a specific media flow.

In an embodiment, an apparatus further comprises wherein the mediadelivery scheduling subsystem detects that a target flow rate for amedia flow has not been met when a deadline for delivery of a nextportion of a media content for the media flow has been missed.

In an embodiment, an apparatus further comprises a plurality of storagedevices, at least a portion of the plurality of storage devices havingdiffering performance characteristics, a media caching subsystem thatstores at least a portion of a media content in a specific storagedevice based at least upon the target flow rate for the media flowassociated with the media content and the performance characteristic ofthe specific storage device, the media caching subsystem instructs thedelivery subsystem to deliver the stored portions of the media contentfrom the specific storage device.

In an embodiment, an apparatus further comprises wherein the flow ratesubsystem determines a target flow rate for a media flow using at leasta measured bandwidth speed of a client system associated with the mediaflow.

In an embodiment, an apparatus further comprises wherein the flow ratesubsystem dynamically determines a target flow rate for a media flowusing at least a dynamic measurement of bandwidth speed of a clientsystem associated with the media flow.

In an embodiment, a method comprises or a computer-readable storagemedium carrying one or more sequences of instructions, wherein executionof the one or more sequences of instructions by one or more processorscauses the one or more processors to perform the steps of: receivingrequests for media content from client systems, calculating a maximumbandwidth and a target flow rate for each outbound media flow,delivering at least a portion of a requested media content to a clientsystem for each outbound media flow, determining when the deliveringstep delivers at least a portion of a requested media content,dynamically adjusting flow rate for each outbound media flow in order tomeet the target flow rate for each outbound media flow, refusingincoming media requests when upon detecting that target flow rates formedia flows may not be achieved if additional media content requests areaccepted.

In an embodiment, a method or computer-readable storage medium furthercomprises wherein the delivering step delivers at least a portion of alower quality media content in order to meet the target flow rate for aspecific media flow.

In an embodiment, a method or computer-readable storage medium furthercomprises wherein the delivering step delivers at least a portion of ahigher quality media content in order to meet the target flow rate for aspecific media flow.

In an embodiment, a method or computer-readable storage medium furthercomprises detecting that a target flow rate for a media flow has notbeen met when a deadline for delivery of a next portion of a mediacontent for the media flow has been missed.

In an embodiment, a method or computer-readable storage medium furthercomprises storing at least a portion of a media content in a specificstorage device, among a plurality of storage devices with at least aportion of the plurality of storage devices having different performancecharacteristics, based at least upon the target flow rate for the mediaflow associated with the media content and the performancecharacteristic of the specific storage device, wherein the deliveringstep delivers the stored portions of the media content from the specificstorage device.

In an embodiment, a method or computer-readable storage medium furthercomprises determining a target flow rate for a media flow using at leasta measured bandwidth speed of a client system associated with the mediaflow.

In an embodiment, a method or computer-readable storage medium furthercomprises dynamically determining a target flow rate for a media flowusing at least a dynamic measurement of bandwidth speed of a clientsystem associated with the media flow.

In an embodiment, an apparatus comprises: a plurality of storagedevices, at least a portion of the plurality of storage devices havingdiffering performance characteristics, a media caching subsystem thatstores at least a portion of a media content in a specific storagedevice based at least upon a performance characteristic of the specificstorage device, the media caching subsystem orders the plurality ofstorage devices in a hierarchical fashion based on bandwidth of eachstorage device among the plurality of storage devices, a storageoptimization subsystem that optimizes bandwidth from each storage deviceamong the plurality of storage devices by dynamically relocatingportions of media content stored on each storage device based on usagemeasurements of the storage device.

In an embodiment, an apparatus further comprises wherein the mediacaching subsystem stores the at least a portion of the media content inthe specific storage device based additionally upon a target flow ratefor the media flow associated with the media content.

In an embodiment, an apparatus further comprises wherein the storageoptimization subsystem relocates a portion of a media content from afirst storage device to a second storage device having betterperformance characteristics than the first storage device based upon anincrease in popularity of the portion of the media content.

In an embodiment, an apparatus further comprises wherein the storageoptimization subsystem relocates a portion of a media content from afirst storage device to a second storage device having lower performancecharacteristics than the first storage device based upon a decrease inpopularity of the portion of the media content.

In an embodiment, an apparatus further comprises wherein the mediacaching subsystem stores multiple portions of media content that includethe at least a portion of the media content in the specific storagedevice when the multiple portions fit in a specifically sized block ofmemory on the specific storage device.

In an embodiment, a method comprises or a computer-readable storagemedium carrying one or more sequences of instructions, wherein executionof the one or more sequences of instructions by one or more processorscauses the one or more processors to perform the steps of: storing atleast a portion of a media content in a specific storage device, among aplurality of storage devices with at least a portion of the plurality ofstorage devices having differing performance characteristics, based atleast upon a performance characteristic of the specific storage device,ordering the plurality of storage devices in a hierarchical fashionbased on bandwidth of each storage device among the plurality of storagedevices, optimizing bandwidth from each storage device among theplurality of storage devices by dynamically relocating portions of mediacontent stored on each storage device based on usage measurements of thestorage device.

In an embodiment, a method or computer-readable storage medium furthercomprises wherein the storing step stores the at least a portion of themedia content in the specific storage device based additionally upon atarget flow rate for the media flow associated with the media content.

In an embodiment, a method or computer-readable storage medium furthercomprises relocating a portion of a media content from a first storagedevice to a second storage device having better performancecharacteristics than the first storage device based upon an increase inpopularity of the portion of the media content.

In an embodiment, a method or computer-readable storage medium furthercomprises relocating a portion of a media content from a first storagedevice to a second storage device having lower performancecharacteristics than the first storage device based upon a decrease inpopularity of the portion of the media content.

In an embodiment, a method or computer-readable storage medium furthercomprises storing multiple portions of media content that include the atleast a portion of the media content in the specific storage device whenthe multiple portions fit in a specifically sized block of memory on thespecific storage device.

6.0 EXTENSIONS AND ALTERNATIVES

In the foregoing specification, embodiments of the invention have beendescribed with reference to numerous specific details that may vary fromimplementation to implementation. The specification and drawings are,accordingly, to be regarded in an illustrative rather than a restrictivesense.

1. An apparatus for simultaneously distributing media across a networkto a plurality of client systems, comprising: a media delivery requestreceiver that receives requests for media content from client systems; aflow rate subsystem that calculates a maximum bandwidth and a targetflow rate for each outbound media flow; a delivery subsystem that, foreach outbound media flow, delivers at least a portion of a requestedmedia content to a client system; a media delivery scheduling subsystemthat determines when the delivery subsystem delivers at least a portionof a requested media content, the media delivery scheduling subsystemdynamically adjusts flow rate for each outbound media flow in order tomeet the target flow rate for each outbound media flow, the mediadelivery scheduling subsystem instructs the media delivery requestsubsystem to refuse incoming media requests when the media deliveryscheduling subsystem detects that target flow rates for media flows maynot be achieved if additional media content requests are accepted. 2.The apparatus of claim 1, wherein the media delivery schedulingsubsystem instructs the delivery subsystem to deliver at least a portionof a lower quality media content in order to meet the target flow ratefor a specific media flow.
 3. The apparatus of claim 1, wherein themedia delivery scheduling subsystem instructs the delivery subsystem todeliver at least a portion of a higher quality media content in order tomeet the target flow rate for a specific media flow.
 4. The apparatus ofclaim 1, wherein the media delivery scheduling subsystem detects that atarget flow rate for a media flow has not been met when a deadline fordelivery of a next portion of a media content for the media flow hasbeen missed.
 5. The apparatus of claim 1, further comprising: aplurality of storage devices, at least a portion of the plurality ofstorage devices having differing performance characteristics; a mediacaching subsystem that stores at least a portion of a media content in aspecific storage device based at least upon the target flow rate for themedia flow associated with the media content and the performancecharacteristic of the specific storage device, the media cachingsubsystem instructs the delivery subsystem to deliver the storedportions of the media content from the specific storage device.
 6. Theapparatus of claim 1, wherein the flow rate subsystem determines atarget flow rate for a media flow using at least a measured bandwidthspeed of a client system associated with the media flow.
 7. Theapparatus of claim 1, wherein the flow rate subsystem dynamicallydetermines a target flow rate for a media flow using at least a dynamicmeasurement of bandwidth speed of a client system associated with themedia flow.
 8. A method for simultaneously distributing media across anetwork to a plurality of client systems, comprising: receiving requestsfor media content from client systems; calculating a maximum bandwidthand a target flow rate for each outbound media flow; delivering at leasta portion of a requested media content to a client system for eachoutbound media flow; determining when the delivering step delivers atleast a portion of a requested media content; dynamically adjusting flowrate for each outbound media flow in order to meet the target flow ratefor each outbound media flow; refusing incoming media requests when upondetecting that target flow rates for media flows may not be achieved ifadditional media content requests are accepted.
 9. The method of claim8, wherein the delivering step delivers at least a portion of a lowerquality media content in order to meet the target flow rate for aspecific media flow.
 10. The method of claim 8, wherein the deliveringstep delivers at least a portion of a higher quality media content inorder to meet the target flow rate for a specific media flow.
 11. Themethod of claim 8, further comprising: detecting that a target flow ratefor a media flow has not been met when a deadline for delivery of a nextportion of a media content for the media flow has been missed.
 12. Themethod of claim 8, further comprising: storing at least a portion of amedia content in a specific storage device, among a plurality of storagedevices with at least a portion of the plurality of storage deviceshaving different performance characteristics, based at least upon thetarget flow rate for the media flow associated with the media contentand the performance characteristic of the specific storage device;wherein the delivering step delivers the stored portions of the mediacontent from the specific storage device.
 13. The method of claim 8,further comprising: determining a target flow rate for a media flowusing at least a measured bandwidth speed of a client system associatedwith the media flow.
 14. The method of claim 8, further comprising:dynamically determining a target flow rate for a media flow using atleast a dynamic measurement of bandwidth speed of a client systemassociated with the media flow.
 15. A computer-readable storage mediumcarrying one or more sequences of instructions for simultaneouslydistributing media across a network to a plurality of client systems,wherein execution of the one or more sequences of instructions by one ormore processors causes the one or more processors to perform the stepsof: receiving requests for media content from client systems;calculating a maximum bandwidth and a target flow rate for each outboundmedia flow; delivering at least a portion of a requested media contentto a client system for each outbound media flow; determining when thedelivering step delivers at least a portion of a requested mediacontent; dynamically adjusting flow rate for each outbound media flow inorder to meet the target flow rate for each outbound media flow;refusing incoming media requests when upon detecting that target flowrates for media flows may not be achieved if additional media contentrequests are accepted.
 16. The computer-readable storage medium of claim15, wherein the delivering step delivers at least a portion of a lowerquality media content in order to meet the target flow rate for aspecific media flow.
 17. The computer-readable storage medium of claim15, wherein the delivering step delivers at least a portion of a higherquality media content in order to meet the target flow rate for aspecific media flow.
 18. The computer-readable storage medium of claim15, further comprising: detecting that a target flow rate for a mediaflow has not been met when a deadline for delivery of a next portion ofa media content for the media flow has been missed.
 19. Thecomputer-readable storage medium of claim 15, further comprising:storing at least a portion of a media content in a specific storagedevice, among a plurality of storage devices with at least a portion ofthe plurality of storage devices having different performancecharacteristics, based at least upon the target flow rate for the mediaflow associated with the media content and the performancecharacteristic of the specific storage device; wherein the deliveringstep delivers the stored portions of the media content from the specificstorage device.
 20. The computer-readable storage medium of claim 15,further comprising: determining a target flow rate for a media flowusing at least a measured bandwidth speed of a client system associatedwith the media flow.
 21. The computer-readable storage medium of claim15, further comprising: dynamically determining a target flow rate for amedia flow using at least a dynamic measurement of bandwidth speed of aclient system associated with the media flow.
 22. An apparatus forsimultaneously distributing media across a network to a plurality ofclient systems, comprising: a plurality of storage devices, at least aportion of the plurality of storage devices having differing performancecharacteristics; a media caching subsystem that stores at least aportion of a media content in a specific storage device based at leastupon a performance characteristic of the specific storage device, themedia caching subsystem orders the plurality of storage devices in ahierarchical fashion based on bandwidth of each storage device among theplurality of storage devices; a storage optimization subsystem thatoptimizes bandwidth from each storage device among the plurality ofstorage devices by dynamically relocating portions of media contentstored on each storage device based on usage measurements of the storagedevice.
 23. The apparatus of claim 22, wherein the media cachingsubsystem stores the at least a portion of the media content in thespecific storage device based additionally upon a target flow rate forthe media flow associated with the media content.
 24. The apparatus ofclaim 22, wherein the storage optimization subsystem relocates a portionof a media content from a first storage device to a second storagedevice having better performance characteristics than the first storagedevice based upon an increase in popularity of the portion of the mediacontent.
 25. The apparatus of claim 22, wherein the storage optimizationsubsystem relocates a portion of a media content from a first storagedevice to a second storage device having lower performancecharacteristics than the first storage device based upon a decrease inpopularity of the portion of the media content.
 26. The apparatus ofclaim 22, wherein the media caching subsystem stores multiple portionsof media content that include the at least a portion of the mediacontent in the specific storage device when the multiple portions fit ina specifically sized block of memory on the specific storage device. 27.A method for simultaneously distributing media across a network to aplurality of client systems, comprising: storing at least a portion of amedia content in a specific storage device, among a plurality of storagedevices with at least a portion of the plurality of storage deviceshaving differing performance characteristics, based at least upon aperformance characteristic of the specific storage device; ordering theplurality of storage devices in a hierarchical fashion based onbandwidth of each storage device among the plurality of storage devices;optimizing bandwidth from each storage device among the plurality ofstorage devices by dynamically relocating portions of media contentstored on each storage device based on usage measurements of the storagedevice.
 28. The method of claim 27, wherein the storing step stores theat least a portion of the media content in the specific storage devicebased additionally upon a target flow rate for the media flow associatedwith the media content.
 29. The method of claim 27, further comprising:relocating a portion of a media content from a first storage device to asecond storage device having better performance characteristics than thefirst storage device based upon an increase in popularity of the portionof the media content.
 30. The method of claim 27, further comprising:relocating a portion of a media content from a first storage device to asecond storage device having lower performance characteristics than thefirst storage device based upon a decrease in popularity of the portionof the media content.
 31. The method of claim 27, further comprising:storing multiple portions of media content that include the at least aportion of the media content in the specific storage device when themultiple portions fit in a specifically sized block of memory on thespecific storage device.
 32. A computer-readable storage medium carryingone or more sequences of instructions for simultaneously distributingmedia across a network to a plurality of client systems, whereinexecution of the one or more sequences of instructions by one or moreprocessors causes the one or more processors to perform the steps of:storing at least a portion of a media content in a specific storagedevice, among a plurality of storage devices with at least a portion ofthe plurality of storage devices having differing performancecharacteristics, based at least upon a performance characteristic of thespecific storage device; ordering the plurality of storage devices in ahierarchical fashion based on bandwidth of each storage device among theplurality of storage devices; optimizing bandwidth from each storagedevice among the plurality of storage devices by dynamically relocatingportions of media content stored on each storage device based on usagemeasurements of the storage device.
 33. The computer-readable storagemedium of claim 32, wherein the storing step stores the at least aportion of the media content in the specific storage device basedadditionally upon a target flow rate for the media flow associated withthe media content.
 34. The method of claim 32, further comprising:relocating a portion of a media content from a first storage device to asecond storage device having better performance characteristics than thefirst storage device based upon an increase in popularity of the portionof the media content.
 35. The computer-readable storage medium of claim32, further comprising: relocating a portion of a media content from afirst storage device to a second storage device having lower performancecharacteristics than the first storage device based upon a decrease inpopularity of the portion of the media content.
 36. Thecomputer-readable storage medium of claim 32, further comprising:storing multiple portions of media content that include the at least aportion of the media content in the specific storage device when themultiple portions fit in a specifically sized block of memory on thespecific storage device.